1. Field
The disclosed embodiments relate to a satellite airbraking airfoil particularly suited to the deorbiting of satellites at the end of their life.
2. Brief Description of Related Developments
At the end of their life, satellites clutter near space and, because at high altitude the air pressure is much reduced, these satellites reaching the end of their service life are liable to remain in orbit for many years and thus clutter space and cause risks of collision and destruction of other satellites.
To fix matters, a satellite with a projected surface area to mass ratio of the order of 5 to 6 thousandths of a m2/kg in orbit at an altitude of 700 km will take of the order of 45 years to descend to an altitude at which it will be destroyed, but certain space agencies now impose a maximum lifetime of 25 years on satellites in low orbit having fulfilled their mission.
Without deorbiting means, this maximum duration would forbid an orbit of greater than 650 km for a satellite having a projected surface area to mass ratio such as defined above.
So, satellite operators endeavor to limit the lifetime of satellites after the end of their service by providing systems which displace them from their orbit so as to deorbit them or position them on a different orbit at the end of their life.
Deorbiting methods are based on the principle of forced re-entry of the satellite into the atmosphere at the end of its life.
Two typical cases arise in general.
Either, according to a first type of orbit, the satellite is on an elliptical orbit possessing a perigee in the dense layers of the atmosphere. In such a case deorbiting takes place naturally in a few days or a few hours.
Or, according to a second type of orbit, the satellite is in a stable orbit not passing through the dense layers and natural deorbiting takes a very long time as seen above.
In the case of a satellite performing its mission in an orbit for which the natural fallout of the satellite is judged to be too distant, the commonest solution for speeding up the deorbiting of the satellite is to lower its orbit by giving it an impulse with the aid of motors.
The drawback is that it is necessary to retain a quantity of fuel, and sufficient energy to allow this impulse, up to an advanced phase of life of the satellite.
Moreover when these motors are not useful to the satellite's mission, they constitute spurious weight when placing the satellite in orbit, as well as useless mass and volume throughout the mission.
Furthermore, this impulse must be implemented although the satellite might now have only a residual functional capability, so it must retain maneuverability beyond its normal lifetime.
An alternative means is airbraking.